Sadly, this doesn't work for me. I don't know why, but the new Google fit app doesn't get all the steps my mi fit app records. Oddly enough, some of them are synced, Google fit even says it got the steps from the mi app.

I tried this but it didn't work for steps. Samsung Health can't receive data about steps from Sleep as Android, but it can send data about steps to Sleep as Android. I went with u/heliummm's solution above. Mi Band Tools is worth it as a paid app though, I can receive notifications on the Mi Band 3 from whichever apps I choose.

What a pitty. I mean why would it, it's a sleep monitoring app. But then I thought it might just synch them all... If I recall correctly, the app even wanted read and write permission for my steps in Samsung health.

One of the reasons why Samsung Health tries to wall itself off from Google Fit and other larger fitness apps is because it would like to build a community that is biased to their licensed brands of telometric gadgets;(eg smartwatches/scales/etc)

In true Samsung fashion, they try to pack in as many features as they can into the Samsung Health app in order to keep it's userbase from looking at other fitness/health tracking apps; and it works, to a certain degree

The problems arise when people want to either switch into or out of that ecosystem, since streak psychology would probably come into play (eg. someone has had 4 years worth of fitness data on his/her app)

While it is true that Samsung Health is jam-packed with comprehensive features and a social aspect that is constantly being improved and polished the Samsung way, but their telometric gadgets (whether it be their watches, earbuds, scales, or what have you) are very pricey compared to their more streamlined alternatives in the market (eg. the Mi Band 3)

So unless you own a Samsung Health-compatible fitness device, or have an entire circle of friends competitively 'streaking' (google streak psychology) their fitness data on the app, Google Fit would be a more universal pick(Google > Samsung in terms of userbase)

On the other hand, people who are from the outside looking into the Samsung Health ecosystem (eg. Mi Fit users who have Samsung Devices), might just want to sync their data into it to join their friends on the social challenges and events on the app;

That or because they want to bring all their data from their previous apps onto Samsung Health in order to switch to it completely

In any case, this isn't the right place to recommend switching to Samsung Health completely

@heliummm just wants to know how syncing the Mi Band 3 to Samsung Health works

I would appreciate a reply on S Health compatibility as well. Huawei also launched an upgrade for their health band, but till these cheap and functional bands are compatible with S-Health, Samsung mobile owners will not benefit much sadly!